PubMed · 15855788
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J M S Pearce. 2005-04-26. Hemianopia.. https://doi.org/10.1159/000085514
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PURPOSE OF REVIEW: Vision restoration therapy has shown promise as a treatment strategy to improve visual field deficits in patients with lesions of the brain or optic nerve. Objective measures of its efficacy, however, have remained controversial. A review of the current theories supporting the reported benefits of vision restoration therapy, and the dissenting opinions, reconsiders vision restoration therapy as an emerging therapy. RECENT FINDINGS: The benefits of vision restoration therapy have been challenged by a study suggesting that no improvement exists with careful control of fixation. Alternatively, others suggest that eye movements are not induced by vision restoration therapy. Functional imaging studies demonstrate the potential role of plasticity in vision restoration therapy. While the exact mechanism remains to be elucidated, subjective improvement in daily functioning is reported in a significant percentage of patients. SUMMARY: Vision restoration therapy is a noninvasive, home-based strategy for the rehabilitation of patients with visual field loss caused by structural or ischemic damage. While subjective benefits in functional status have been reported by patients following completion of the program, debate centers around the inadequacy of the methods used to document its efficacy. Until such a method is validated by carefully controlled studies, subjective improvement in visual function stands alone as evidence of vision restoration therapy's benefit.
PURPOSE OF REVIEW: The aim of this article is to review the controversial findings for NovaVision's vision restoration therapy. RECENT FINDINGS: It has been claimed that NovaVision's computerized therapy results in expansion of the visual field in optic nerve and occipital lesions, but the outcome has been challenged on the grounds of unsatisfactory perimetric control of central fixation and disputed mechanisms. SUMMARY: In clinical practice NovaVision's therapy should not currently gain acceptance in view of unacceptable perimetric standards and equivocal results. Possible effects on a relative scotoma at the edge of a lesion have not been adequately explored. In the interim, research should also be focused on compensatory eye movement strategies.
The association between bitemporal hemianopia and chiasmal compression is well recognized. The majority of chiasmal syndromes are caused by extrinsic compression from pituitary tumors, suprasellar meningiomas, craniopharyngiomas, and aneurysms. However, it is not clear why compressive lesions of the chiasm show a predilection for damage to nasal fibers with bitemporal hemianopia. Few experimental attempts at elucidating these mysteries have been reported and none has provided an adequate explanation. The authors postulate that the susceptibility of nasal fibers to preferential damage is explained by structural collapse theories as applied to crossing and noncrossing cylinders. By constructing a simplified mathematical model, the authors demonstrate that nasal fibers are subject to relatively greater pressures for any given external compressive force acting on the chiasm.